Our guide to successful sequels

1. ROUND UP THE USUAL SUSPECTS Familiarity breeds success, so even though it will cost you, lure back the original stars. Lethal Weapon 3 not only reteams Mel Gibson and Danny Glover, but also cobills Joe Pesci, who stole the show in Lethal Weapon 2. 1982’s Grease 2, however, starred then-unknown Michelle Pfeiffer and still-unknown Adrian Zmed in lieu of John Travolta and Olivia Newton-John. It flunked out fast.

2. DON’T DAWDLE Sequels shouldn’t be confused with high school reunions — if you wait too long to get the gang back together, memories may well have faded. The Two Jakes, released 16 years after 1974’s Chinatown, couldn’t rekindle the old passions. A three-year separation is ideal: The first movie will be out on video, the contracts for No. 2 will finally have been negotiated, and there will be just enough time left to rush a sequel through production.

3. UP THE ANTE Sequels must repeat the winning formula of their parent movies, but since audiences still want to fell they’re getting something new, goose up the effects. Director James Cameron played the idea of pitting two terminators — a good Schwarzenegger and a bad Schwarzenegger — against each other in T2, but then he came up with the liquid t-1000, a dazzling special-effects creation that made something old seem new again.

4. DON’T GET ARTY Francis Coppola’s Godfather II was one of the few sequels that was artistically superior to its inspiration. Resist the temptation to try to do the same. Executive producer George Lucas’ More American Graffiti went bust when it experimented with four different film styles, and William Peter Blatty’s The Exorcist III stiffed by offering a philosophical debate on good and evil when all folks wanted was more pea soup.

5. REMEMBER, VIDEO HELPS Even if a movie doesn’t rake in huge bucks, it’s still a sequelizer candidate if it does well on video. How else to explain this summer’s Aces: Iron Eagle III, except to say that Iron Eagle II sold $21 million worth of tapes? Don’t ignore video’s promotional value, either: The new Alien/Aliens Triple Pack, with the first two movies (that’s No. 1) plus a peek at Alien 3, is an ad waiting to be rented.

6. BE PREPARED TO PAY MORE… As talent, effects, and locations get pricier, the budgets for sequels soar. Consider the Rocky saga. Made for just $1 million, 1976’s Rocky was a lean, mean contender. Rocky II in 1979 weighed in at $7 million; 1982’s Rocky III at $17 million; 1985’s Rocky IV at $30 million; and 1990’s finale, Rocky V (for which Stallone knocked down $20 million), $42 million. That’s right-42 times the original.

7. AND EARN LESS Just as the cost of making a sequel rises, the box office returns can be expected to decrease. Don’t be greedy: Lucky is the sequel that grosses 50 percent of its original. And many don’t even do that: Three Men and a Little Lady did 32 percent of the box office toted up by Three Men and a Baby; Gremlins 2: The New Batch did 28 percent of Gremlins’ business; and Look Who’s Talking Too did a mere 20 percent of No. 1.

8. DON’T COUNT YOUR CHICKENS Most contracts include provisions for possible sequels, and most endings leave the door open for further adventures. But don’t buy that Montana ranch until you see how the original performs. Just ask Dino De Laurentiis, who thought he was birthing a Star Wars dynasty with the impenetrable Dune. Or Kathleen Turner, who figured she’d crack case after case as V.I. Warshawski. Case closed.